空调系统冷冻水循环水泵变频运行的变温差控制

在分析空调系统变流量运行调节的基础上,提出了变温差控制并给出了控制方案。变温差控制过程不仅具有负反馈,而且具有正反馈,能较好的适应空调负荷的变化。比较分析了变温差控制、定温差控制、定压差控制的节能性,变温差控制的节能潜力最大,是一种最佳控制方式。     

北京市PM5.0可吸入颗粒物反演及其时空分布分析

分析城市可吸入颗粒物的空间特征及影响因素对于制定更为有效的可吸入颗粒物污染控制政策具有重要的现实意义.本研究在实际采样和遥感数据处理基础上,构造差值植被指数(DVI),通过建立TM影像与对应PM5.0颗粒物实测值之间的相关关系模型,对北京市2008~2010年3 a的PM5.0的分布进行了反演计算和精度分析;研究了NDBI和NDMI对PM5.0浓度的影响,进一步揭示了北京五环区域范围内可吸入颗粒物的时空分布特征.结果表明,采用DVI反演PM5.0分布的方法可行,反演精度在可接受范围内;整体上研究区2008年PM5.0颗粒物污染最轻,西南三环和四环以及东南三四环之间为颗粒物污染的高值区,西北五环附近颗粒物污染较轻;NDBI(归一化建筑指数)、NDMI(归一化水汽指数)与PM5.0可吸入颗粒物的分布分别呈现显著的负相关和正相关关系,且二者对PM5.0的影响相近.     

铅低累积玉米品种的筛选研究

通过田间实验,研究了在高浓度Pb （2000mg/kg）胁迫下,25个玉米品种生长、产量变化及根、茎叶和籽粒Pb含量的差异。结果表明：在同一污染条件下,25个玉米品种生长对Pb的响应存在显著差异;不同品种根、茎叶和籽粒对Pb吸收、累积及分配能力存在显著差异,分配规律为：根＞茎叶＞籽粒;通过聚类分析获得对Pb耐性较高的品种6个、籽粒Pb低积累的品种6个;综合分析,最终筛选出寻单7号为Pb低累积品种。     

大渡河干海子滑坡稳定性研究

干海子滑坡位于大渡河流域,规模巨大.为研究该滑坡的稳定性,在对滑坡基本特征及变形破坏特征等深入研究的基础上,采用极限平衡法(Geo-slope软件)和有限差分法(FLAC-3D软件)对该滑坡的稳定性和应力应变特征进行了计算、模拟.稳定性计算模拟主要从深层、浅层及局部稳定三方面入手分析,计算模拟结果与滑坡的宏现地质现象均...     

船舶涂料海洋大气暴露与室内加速试验模拟性研究

通过两年海洋大气环境暴露试验、盐雾／紫外冷凝老化交替试验和氙灯老化试验。对比聚氨酯涂料、丙烯酸涂料涂层的色差和失光率,研究了3种试验对涂层表观性能的影响。发现紫外／冷凝老化加速试验对海洋大气暴露试验有很好的模拟性。     

长江经济带绿色城镇化效率评价及其影响因素——基于多维城镇化视角

本文引入资源和环境因素,以城镇化综合指数为期望产出,运用SBM方向性距离函数测算了2010—2020年长江经济带112个地级市（州）的绿色城镇化效率,并采用空间面板模型和地理探测器对绿色城镇化效率的影响因素进行实证分析。结果表明：长江经济带绿色城镇化效率整体水平不高,下游地区绿色城镇化效率高于上游和中游地区,资源消耗和环境污染是效率损失的主要来源;绿色城镇化效率表现出较为明显的热点—次热点—次冷点—冷点自东向西的带状分布格局,存在显著的空间正相关性。政府财政支出对绿色城镇化效率产生负向影响,外商直接投资和产业结构对提升绿色城镇化效率有显著的促进作用,且三者的影响具有地区差异性;市场力因素有利于绿色城镇化效率的提高。邻近城市间绿色城镇化效率的空间溢出效应明显,且空间溢出效应是长江经济带绿色城镇化效率空间差异的最主要因素,各因素的影响具有协同增强的作用。     

路堤荷载下带桩帽刚性桩复合地基桩土应力比分析

路堤一般由填土、碎石等散体材料组成,刚性桩复合地基中,桩土刚度差异较大引起的桩土间沉降差异,会导致路堤内部出现相对竖向位移。通过路堤填土的受力平衡分析,根据桩土差异沉降,求解出桩帽和桩帽间土体的应力分配,并结合桩帽下应力分配得出桩身应力,最终求解出桩土应力比及桩的荷载分担比例。工程实例监测结果验证了文中计算公式的适用性和可靠性。通过分析计算结果和实测结果,得出了一些路堤荷载下刚性桩复合地基的承载规律,可供理论研究和工程设计参考。     

Effects of the new nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on nitrate and potassium leaching in two soils

In this study, soil column was used to study the new nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on nitrate (NO3--N) and potassium (K) leaching in the sandy loam soil and clay loam soil. The results showed that DMPP with ammonium sulphate nitrate (ASN) ((NH4)2SO4 and NH4NO3) or urea could reduce NO3--N leaching significantly, whereas ammonium (NH4 -N) leaching increased slightly. In case of total N (NO3--N NH4 -N), losses by leaching during the experimental period (40 d) were 37.93 mg (urea), 31.61 mg (urea DMPP), 108.10 mg (ASN), 60.70 mg (ASN DMPP) in the sandy loam soil, and 30.54 mg (urea), 21.05 mg (urea DMPP), 37.86 mg (ASN), 31. 09 mg (ASN DMPP) in the clay loam soil, respectively. DMPP-amended soil led to the maintenance of relatively high levels of NH4 -N and low levels of NO3--N in soil, and nitrification was slower. DMPP supplementation also resulted in potassium leached less, but the difference was not significant except the treatment ASN and ASN DMPP in the sandy loam soil. Above results indicate that DMPP is a good nitrification inhibitor, the efficiency of DMPP seems better in the sandy loam soil than in the clay loam soil and lasts longer.     

Urban Energy Efficiency from Cities in China and Policy Implications

Using 1995-2006 panel data for 210 cities, this article firstly measures total factor energy efficiency for Chinese cities with constant return to scale data envelopment analysis model,and then describes the features of regional differences. The results show that the changing trend displays four "reversed U" shapes. A turning point of widening gap occurred among cities in 2000 and there was a certain convergence among four regions. Urban energy efficiency level is unstable. Cities with low efficiency and high energy input will be the focus of energy-saving and reducing emissions. According to Tobit model, resource endowment, temperature, industrial structure, technology level and variety of policy factors should be treated differently in different situations.     

The determination and matching analysis of pinch point temperature difference in evaporator and condenser of organic rankine cycle for mixed working fluid

Exergo-economic analysis of the pinch point temperature difference (PPTD) in both evaporator and condenser of sub-critical organic Rankine cycle system (ORCs) are performed based on the first and second laws of thermodynamics. Taking mixture R13I1/R601a as a working fluid and the annual total cost per net output power Z as exergo-economic performance evaluation criterion, the effects of PPTD in evaporator ΔT_e, and the PPTD ratio of condenser to evaporator y, on the exergo-economic performance of ORCs are analyzed. Moreover, how some other parameters influence the optimal PPTD in evaporator ΔT_e,opt and the optimal PPTD ratio of condenser to evaporator y_opt are also discussed. It has been found that the exergo-economic performance of ORCs is remarkably influenced by ΔT_e and y, and there exists ΔT_e,opt and y_opt. In addition, ΔT_e,opt and y_opt are affected by heat transfer coefficient ratio of condenser to evaporator ß, the temperature of working fluid at dew point in condenser T_1a, and composition of R13I1/R601a: larger ß and T_1a lead to lower ΔT_e,opt and y_opt; by contraries, larger mass fraction of R13I1 makes ΔT_e,opt and y_opt increase, and y_opt increases linearly. The effects of the temperature of working fluid at bubble point in evaporator T_3a, mass flow rate of exhaust flue gas m_g, and inlet temperature of exhaust flue gas T_gi on ΔT_e,opt and y_opt are very slight. For comparison, three additional working fluids, namely R601a, R245fa, and 0.32R245fa/0.68R601a, are also taken into account.